After constructing the reservoir and installing the sluice gate, Jin began excavating toward the water vein.
"Dig. Toughening."
Jin reinforced the borehole as he dug. Within about two minutes, water welled up to the surface.
"Ohh?!"
(That went well.)
In truth, the water vein Jin had tapped this time was under pressure.
Several subterranean water veins flowed from Lake Kotsushi, and those that had existed from the beginning—before the Progenitors had modified them—retained enough pressure to flow freely to the surface as artesian wells.
Consequently, they ran deep underground, making them impossible to reach without Jin's level of skill and knowledge.
Considering the volume of water carried by the vein, the recent rainfall and the forecast of increased annual precipitation were what had prompted Jin to proceed with the excavation.
If they were to add more reservoirs in the future, they would not be able to rely solely on such naturally flowing veins, so Jin and Laojun believed automated pumps would likely be required in those instances.
(Still, letting it flow naturally works just fine here for now.)
The volume of gushing water was neither too much nor too little—roughly 1,000 liters (one cubic meter) per minute.
The capacity of the reservoir he had constructed was 1,350 cubic meters. In other words, it was calculated to fill completely in 1,350 minutes, or 22.5 hours.
With nearly a full day until it reached capacity, Jin D had plenty of time.
First, he dug a channel leading toward the village and made a separate small reservoir.
From there, he branched channels in three directions, excavating small reservoirs at the ends of those as well.
The reservoirs at the very ends served as irrigation ponds.
Assisted by Reiko and Hope, Jin D completed all of this earthwork before noon.
"That should do it."
The main reservoir was still far from full.
"Next, I should make sure it won't overflow, just in case."
It was less than thirty kilometers from Saichi Village to the sea.
Jin D decided to dig a drainage channel leading all the way to the ocean.
For this, he resolved to use the Smiths.
Under the pretense that they had been brought aboard the Hurricane in advance, he summoned ten Smiths from Hourai Island.
They excavated a trench, carefully steering clear of fields and orchards. The trench measured two meters wide and one meter deep.
The Smiths dug at a rate of ten meters per minute.
For a thirty-kilometer channel, the math meant it would be finished in fifty hours—a little over two days.
"..."
"......"
Faced not only with Jin but also with the absurd, extraordinary capabilities of the golems under his command, the village chief and the undersecretary were left utterly speechless.
After eating a light lunch just for appearances, Jin D got to work on the next task: installing an incinerator.
Most organic waste could simply be composted, but the soil in this region was already fertile enough that there was little need for it.
Rather, the primary purpose was to prevent unsanitary garbage from piling up and becoming a breeding ground for mold and pathogens.
Jin also thought it would be ideal if the unit could eventually burn the sludge that accumulated in the drainage channel's settling basin.
"Metal really is the best choice, after all."
Since some materials required high-temperature incineration, stone structures left room for concern.
In the case of natural rock, which was an aggregate of various mineral grains, exposure to high temperatures could cause heat-sensitive minerals to shatter or break the bonds between particles, making the stone brittle.
Granite, composed of quartz, mica, and feldspar, was known to crack at around 500 degrees Celsius.
Marble was said to turn to powder at around 800 degrees Celsius, suggesting that roughly 1,000 degrees Celsius was the upper threshold for fire-resistant stone.
Many materials known as synthetic, calcined fine ceramics possessed exceptional heat resistance.
Alumina (aluminum oxide) was said to withstand temperatures up to roughly 2,000 degrees Celsius.
However, a drawback of ceramics was their brittleness; despite their hardness, they were prone to chipping and unsuitable for rough handling.
Therefore, Jin decided to take iron, which had a melting point of 1,538 degrees Celsius, and apply Toughening and Stabilize to reinforce its molecular structure, forging what could essentially be called Magi Steel.
"Roughly speaking... I wonder if it can withstand up to around 3,000 degrees?"
Because Jin had processed it in complete earnest, it ended up possessing such extreme physical properties.
Along with its enhanced heat resistance, its tensile strength was roughly double that of ordinary steel, meaning it would never break under routine use.
Including the chimney portion, it stood three meters tall. The main body measured 1.5 meters high, one meter wide, and one meter deep.
In appearance, it differed little from a metal incinerator one might find in modern Japan.
However, a variety of maintenance-free features had been engineered into it.
It was designed so that even in Jin's absence, improper use would not cause it to break down.
"Please burn any unwanted garbage in this."
Incidentally, it was equipped with a heating unit that utilized a fire-attribute magi-crystal, requiring no fuel whatsoever.
Furthermore, it automatically regulated the optimal combustion temperature for whatever refuse was placed inside, leaving behind virtually no unburnt residue.
If possible, he had wanted to channel the waste heat into boiling water or other utilities, but he decided to put that aside for now.
"...And that covers the basics. Please feel free to use it for whatever you need."
"..."
"......"
As he concluded the explanation, the village chief and the undersecretary were once again struck completely dumb.
By the time he finished explaining how to operate the incinerator, it was only two in the afternoon.
"...I should make a hot spring after all... No, let's build a public bathhouse."
While taking a bath served no functional purpose for Jin D (aside from washing away dirt), Jin himself, who was remotely operating the automaton, simply wanted to build one.
Incidentally, due to chronic water shortages throughout the Four Principalities, people had no custom of taking baths, except for those living near Lake Kotsushi and Lake Yato.
At most, nobles might soak in hot water once every few days.
Wiping one's body down with warm water was considered a luxury, while commoners made do with cold water even during the winter (though the minimum temperature rarely fell below 20 degrees Celsius).
While that might have been manageable in the previously arid climate, demand for baths was bound to increase as rainfall picked up and humidity rose.
Thus, Jin sought to establish a public bathhouse as part of the village's model district.
Keeping the body clean played an essential role in preserving health and preventing disease.
"I suppose I'll go with a magic-circle-type bath boiler."
It could be produced at low cost, which made it well-suited for widespread adoption.
Just like the reservoir, naturally pressurized groundwater would be heated and allowed to flow continuously through the tub.
"Instead of pouring it in from above, it might be better to have it well up from the bottom."
That offered the added benefit of keeping sediment from settling.
"The wastewater can just connect to the drainage channel via a septic tank."
He also opted to equip the septic tank with a magic-circle-based purification system.
Although it ran on a magic circle, the pattern was engraved onto a bronze plate and sealed under quartz glass, rendering it virtually immune to age-related wear.
By Jin and Laojun's estimates, it would function reliably for around fifty years.
That was more than enough to maintain a constant supply of heated, free-flowing water for a bathhouse like this.
Due to material constraints, building the changing rooms and surrounding facilities was postponed until the following day.
"With this, you'll be able to bathe every single day."
"Ohh! This is simply magnificent!!"
Village Chief Aik beamed with delight, while Ministry of Technology Undersecretary Nahams Marow stared at the boiler and asked,
"...Jin-dono, can this be mass-produced?"
The look on his face made it obvious he wanted similar facilities constructed in the royal capital of Resonare as well.